Asking for my son

My son is 12 and I want to do what I can to help boost his confidence. Lately he has been showing interest in how he looks and seems to be liking certain clothes. The problem is that sometimes it is hard to find what will look nice on him due to a medical condition where he has three enlarged organs. This makes his stomach look large. He seems to be fond of sweaters, hoodies, and button ups.

So my question is what would suggest for his scenario? And what fashion advice would you give to your 12 y.o. self?